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Cancelling default behavior

From: JavaScript: Events

Video: Cancelling default behavior

A lot of events have default behaviors that take place when the events happen. So for example when we click on a link, the default behavior is to follow that link probably onto a website. Or when the user tries to submit a form, the default behavior is to take the form data and pass it to a form processor. You might want to stop the data from being passed to the form processor, so you can do your own validation. In order to control how an event reacts with default behavior, we use a method called prevent default. So, let's take a look at how that works. So, here I am on my form and what I want to do is add an anchor tab to all these elements.

Cancelling default behavior

A lot of events have default behaviors that take place when the events happen. So for example when we click on a link, the default behavior is to follow that link probably onto a website. Or when the user tries to submit a form, the default behavior is to take the form data and pass it to a form processor. You might want to stop the data from being passed to the form processor, so you can do your own validation. In order to control how an event reacts with default behavior, we use a method called prevent default. So, let's take a look at how that works. So, here I am on my form and what I want to do is add an anchor tab to all these elements.

So, I'm going to use a kung fu Sublime Text 2 technique. So, hold down the Alt key or the Option key on a Mac and click and drag it to select all these elements. And I'm going to hold down the Cmd+Shift key because I'm on a Mac and hit the right arrow. That's going to select everything from that point to the end of the line. Then I'm going to hold down the Option and Shift key and go to the left a couple of times. But that will do a select everything except for the last few characters. So then I'm going to say cut and then am going to add an anchor tag right here and hit tab.

And now I get a bunch of anchor tags, and then I'm going to type in some URL here. So, I'll do my blog. And then I will hold down the Alt key and click and drag right here, and then paste all of my images back there. So this is pretty much the same thing as before, except that we've wrapped our images with the anchor tag. So what I want to do is prevent the event from going to the website and I can do that by using the prevent default method. So I'll do e.preventDefault and I'll copy that also into my pink element right here.

So I'm going to save this and now when I go back into my page if I refresh and click on any of these, it's going to capture the event and it's going to display the event information on the console. It's not going to go to a website. So let me go ahead and take that off, so I'll take both of these preventDefault methods off, and I'll save it, and come back here, and I'll refresh, and I'm going to click on these, and it's actually going to take me to that website. So let me go back into my code and leave those in. So prevent default can be really useful for things like form processing and validation.

If you want to learn more about forms, make sure you check out my course on validating and processing form with JavaScript and PHP.

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JavaScript: Events

27 video lessons · 6993 viewers

Ray Villalobos
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